Heat actuated steering mount for maintaining frequency alignment in wavelength selective components for optical telecommunications

Abstract

A simple and robust heat actuated steering device for use with mirrors and other optical components of optical telecommunications equipment is described, together with systems which implement such devices. The device uses differential heating between two legs of a flexured mount to allow tilting that can be used to steer an optical beam. Disturbances in the optical alignment, caused by temperature changes, of an optical device containing this component can be compensated by measuring the device temperature and using this to determine a command signal, for example as provided through a lookup table, to correct for device misalignment. Techniques for calibrating the device and establishing the correction data are also disclosed.

1. A system for compensating for thermally-induced alignment errors in free-space optical systems comprising
 an input port adapted to receive an input beam, 
 a mount, 
 an optical element, intended to be in optical alignment with the input beam during operation, affixed to the mount, 
 a heater for causing the mount to flex in response to variations in temperature to maintain optical alignment between the input beam and downstream components. 
 
   
   
     2. The system of  claim 1  wherein the optical element is one of a group comprising a mirror, a collimator, a wavelength dispersion element, and a MEMS element. 
   
   
     3. The system of  claim 1  wherein the optical element is a mirror. 
   
   
     4. A mount for compensating for alignment errors in a free space optical path caused by temperature variations comprising
 a base, 
 a crossmember adapted to receive an optical element, 
 a first leg, 
 a second leg, 
 a heater associated with the first leg for selectively heating the first leg relative to the second leg to adjust the position of the optical element. 
 
   
   
     5. The mount of  claim 4  wherein the mount is constructed of a single material. 
   
   
     6. The mount of  claim 5  wherein the material is one of a group comprising stainless steel, Kovar and aluminum. 
   
   
     7. The mount of  claim 4  wherein the heater is a resistor. 
   
   
     8. The mount of  claim 7  wherein the heater is affixed to the first leg. 
   
   
     9. The mount of  claim 4  further comprising a temperature sensor for detecting ambient temperature. 
   
   
     10. The mount of  claim 9  further including a selectively variable electrical power source responsive to the temperature sensor for adjusting the heater. 
   
   
     11. The mount of  claim 4  wherein the first leg includes at least one narrowed region. 
   
   
     12. The mount of  claim 4  wherein the first leg includes two narrowed regions for providing thermal isolation of the first leg relative to the second leg. 
   
   
     13. The mount of  claim 4  wherein the mount is constructed of more than one material. 
   
   
     14. The mount of  claim 4  wherein the optical element is one of a group comprising a mirror, a collimator, a wavelength dispersion element, and a MEMS element. 
   
   
     15. A method for calibrating a mount capable of adjusting the position of an optical element mounted thereon in response to applied voltages comprising
 adjusting the ambient temperature of the mount to a first predetermined temperature, 
 applying a first amount of electrical power to the mount, 
 recording an indicia representative of the change in position of the associated optical element in response to the first amount, 
 applying a second amount of electrical power to the mount, 
 recording an indicia representative of the change in position of the associated optical element in response to the second amount, 
 repeating the adjusting, applying and recording steps for a predetermined number of temperatures and voltages, 
 storing the indicia representative of the change in position responsive to each amount of applied power at the various predetermined temperatures. 
 
   
   
     16. A method for maintaining optical alignment within a free space optical system susceptible to temperature-induced alignment errors comprising
 providing an input beam, 
 positioning an optical element in free space optical alignment with the input beam, 
 affixing the optical element onto a mount responsive to differential heating to adjusting the position of the optical element in at least one dimension, and 
 adjusting the differential heating of the mount in response to variations in ambient temperature.